The invention relates to a shift drum for use in a suction pipe arrangement for a multi-cylinder internal combustion engine with an induction distributor and with first individual suction pipes arranged side by side and ending in a flange and with second individual suction pipes.
DE 197 12 680 discloses a shift drum for use in a suction pipe arrangement for a multi-cylinder internal combustion engine with first individual suction pipes arranged side by side and second individual suction pipes located in the interior. This shift drum is inserted into a longitudinal bore, which intersects at least the first or the second individual suction pipes and which has a sealing element mounted thereto for each individual suction pipe. This sealing element comprises two sealing strips, which at their ends are connected with two ring elements. The sealing strips lie resiliently against the inlet or outlet opening of the longitudinal bore which contains the shift drum.
The one-part design of the sealing element makes it possible to combine the axial and radial seal in one component. But this constitutes only a compromise solution for the two sealing situations. In the one-part design, the axial sealing strips cannot be mounted without play because they adjoin the radial sealing areas. This causes air leakage flow between the sealing element and the shift drum. A further drawback of the one-part design of the sealing element is the mutual double seal of two adjacent individual suction pipes arranged side by side. Since each sealing element comprises two radial sealing areas, whereas a single radial component would be sufficient mutually to seal the individual suction pipes, a greater overall volume is required. In addition, due to the complex geometry of the sealing element, the injection mold is complex and costly.
DE 44 23 427 discloses an induction system for a multi-cylinder internal combustion engine with first and second individual suction pipes of different length. Said first and second individual suction pipes are arranged side by side. The first individual suction pipes are separated from the second individual suction pipes by a shift drum. To seal adjacent individual suction pipes, piston ring type sealing elements are mounted to the shift drum, so that a piston ring separates two adjacent individual suction pipes from one another. In this embodiment, however, no axial sealing elements are provided to separate the first from the second individual suction pipes. To improve the charging effect by the negative pressure wave, which is produced by opening the valves on the cylinder block, a seal between the first and the second individual suction pipes is required.
The object of the invention is to create a sealing body, which has good sealing properties, requires little mounting space, and ensures cost-effective production. This object is attained by the invention as described and claimed hereinafter.
The shift drum according to the invention, due to its arrangement in a longitudinal bore, is particularly suitable mutually to seal individual suction pipes arranged side by side, which are intersected by the longitudinal bore. To this end, radial sealing means are used, which are dimensioned in such a way that in their mounted state they fit against the longitudinal bore surrounding the shift drum to form a seal. The radial sealing means may also rotate together with the shift drum.
In the suction pipe arrangement with first and second individual suction pipes of different lengths, a channel may be closed off by means of the shift drum disposed in the longitudinal bore. To this end, said shift drum comprises separate seals mounted to the shift drum, which in closed position, seal the associated individual suction pipes with respect to one another. Said seals directly adjoin the radial sealing means. They may have a wide variety of contours; e.g., the sealing-surfaces may be angled with respect to the shift drum axis to obtain additional guidance of the shift drum within the longitudinal bore. Each of the first individual suction pipes has its own seal, which is independent from the individual suction pipe arranged adjacent thereto. Separating the axial from the radial sealing function makes it possible optimally to tune the two components to their function. For fixation to the shift drum, the seal no longer requires elements clasping the periphery of the shift drum, since the seal may be attached to the shift drum, for instance by gluing.
In a special embodiment, the seal has two axially effective sealing surfaces. The sealing surfaces of the seal are arranged in such a way that in a closed position, the individual suction pipe is sealed by the sealing surfaces, and the axial sealing surfaces directly adjoin the radial sealing means.
According to a further embodiment, the seal has a prestressing area. This area is stretched during installation, so that the seal can be mounted to the shift drum. In the assembled state, a certain prestressing force remains which causes the seal to remain at its prescribed location and to perform its sealing function. The prestressing area may be designed, for example, as a shaped spring, a curved spring, or a rubber lip.
In a special embodiment, the seal is positively locked, for instance by clipping or latching. To this end, the shift drum has a holder for the seal. This holder is configured in such a way that partial areas of the seal are enclosed to fix the seal to the shift drum when mounted. This holder may take the form of, for example, hooks or grooves.
An advantageous further embodiment of the inventive concept is to use a seal with a flow cap, which positively influences the course of the flow along the sealed opening of the individual suction pipes to prevent turbulence. This flow cap may be mounted as a separate component to a sealing contour of the seal, e.g. by gluing, welding, screwing or snapping. The flow cap may furthermore be made of a different material than the sealing contour.
A special embodiment of the invention envisions forming the seal directly on the flow cap. This may be accomplished by injection molding. If configured accordingly, the flow cap may also perform the role of the prestressing area.
A further variant of the invention is to provide the seal with clamp clips, which are used to mount the seal to the shift drum and which enclose only a partial area of the shift drum periphery. The seal may be clamped to the shift drum by means of these clamping clips. Another alternative to attach the seal is to place it on the shift drum and then to insert this preassembled unit into the longitudinal bore. Insertion of the shift drum causes the individual seals to be pressed firmly against the shift drum so that they are fixed.
To this end, it is advantageous to mold an elastomer to the seal. The elastomer is compressed during installation and is thus prestressed. This separates the individual suction pipes while producing a seal. Furthermore, the elastomer can compensate for manufacturing tolerances as well as the relaxation of the sealing element.
According to a further embodiment of the invention, the seal is configured in such a way that it completely encircles and seals the opening in the shift drum. To obtain a complete seal of the shift drum, two sealing elements are required, which seal the opening in the shift drum of each individual suction pipe.
It is advantageous to make the seal of synthetic resin material, so that even complex contours can be produced. Synthetic resin material furthermore has good sealing and frictional properties.
These and other features of preferred further developments of the invention are set forth in the claims as well as in the description and the drawings. The individual features may be implemented either alone or in combination in the embodiment of the invention or in other fields of application and may represent advantageous embodiments that are protectable per se, for which protection is herewith claimed.